1. Field of the Invention
The present invention is directed to a method of magnetically loading a sintering material into a Dwight-Lloyd sintering apparatus in which a sintered ore is produced as one of the sintered materials for use in a blast furnace. The invention has particular reference to a method wherein magnetically susceptible sinterable substances such as ferrous metal-rich mill scale, calcium ferrite-containing returned ore and the like, and fine or particulate sinterable substances are charged on a pallet mounted on the sintering apparatus in such a manner that the two different types of substances are segregated in large amounts in an upper portion of a sintering material layer deposited on the pallet.
2. Description of the Related Art
In the production of a sintered ore using a sintering apparatus of a Dwight-Lloyd type (referred to hereinbelow as a DL sintering apparatus), ferrous metal-containing iron sources such as particulate iron ore, iron sand, mill scale and the like are first intermixed with secondary materials such as limestone, serpentine, returned ore and the like and further with fuel sources such as coke dust, gas ash and the like, whereby a sintering material is prepared which is then adjusted in its water content to about 7% and placed in granulated form. As shown in FIG. 28 of the accompanying drawings, a sintering material 2 that has been put in an ore supplying hopper 1 mounted on a DL sintering apparatus is cut by means of a drum feeder 3 and supplied to a sloping chute 4 of a plate type. The sintering material 2 is segregated in regard to its particle sizes upon percolation (filtration or penetration) when it is slidably dropped out of the sloping chute 4, and hence, such sintering material becomes rich in fine sinterable substances in its lower layer portion and rich in coarse sinterable substances in its upper and intermediate layer portions.
The sintering material 2 thus segregated upside down is subjected to inverse segregation of the particle sizes when it is charged from a lower end of the sloping chute 4 to a pallet 5 disposed to continuously travel in an arrowed direction. Thus, a sintering material layer 7 of a given thickness is formed with relatively fine sinterable substances segregated in its upper portion and relatively coarse sinterable substances segregated in its intermediate and lower portions. The sintering material layer 7 is subsequently ignited on its surface portion with a pilot burner (not shown) and sintered, while the pallet 5 is caused to move toward a rear end of the sintering apparatus, with air above the layer 7 being suctioned downwardly of a grate bar located on the pallet, the suctioning being conducted by the use of an exhauster (not shown). In this way, a sintered ore is produced.
In the sintering operation, the particle size distribution and compositional distribution of a sintering material deposited to correspond to the height of a sintering material layer bring about an important effect on successful sintering. Namely, at an initial stage of ignition in an igniting furnace, air is allowed to pass through the sintering material layer 7 from its ignited surface to its bottom upon suction at a lower part of the pallet 5. In this course of sintering, air of normal temperature is supplied without preheating to a sintered melt zone (for example, a region of higher than 1,200xc2x0 C.) that has been defined in an upper portion of the sintering material layer 7. At middle and last stages of sintering, however, air to be suctioned downwardly of the layer 7 is passed through a completely sintered region in that upper portion and hence preheated, followed by feeding to sintered melt zones defined in the intermediate and lower portions of the layer 7.
Consequently, the upper portion of the sintering material layer is lower in the bulk temperature and besides shorter in the length of time for exposure to elevated temperature than the intermediate and lower portions. This leaves the problem that a sintered ore formed in the upper portion is low in melt bonding and hence small in mechanical strength with reduced sintering yield.
In recent years, as a certain method of the loading of a sintering material, segregation loading has been highly reputed in which the particle size distribution and carbon content of a sintering material layer deposited on a pallet can be varied at will. Such method has been found effective in alleviating the problems discussed above.
Japanese Unexamined Patent Publication No. 61-223136 discloses, for instance, that a sintering material layer to be formed on a pallet should be reduced in its density by means of a screen constituted with a plurality of wire materials extending along a flow of sintering material being loaded on the pallet, and at the same time, the sintering material should be segregated with fine particles held in an upper layer and with coarse particles held in intermediate and lower layers so as to make the upper layer highly permeable to air with eventual improvement of yield and productivity of a sintered ore. This prior art method, however, has the problem that since a sintering material of 7% or so in water content is prone to get adhered to the wire materials, the resultant sintering material layer is difficult to stably retain in a segregated state as originally desired.
Japanese Unexamined Patent Publication No. 63-263386 discloses that a sintering material layer to be formed on a pallet should be reduced in density with fine particles segregated in an upper layer portion and with coarse particles segregated in a lower layer portion by use of a plurality of wires disposed perpendicular to a flow of sintering material being loaded on the pallet and by proper adjustment of the wire-to-wire openings to thereby improve the yield and productivity of a sintered ore owing to increased air permeability in the upper layer.
Such known method is contrived to remove part of the sintering material having been adherent to the wires by causing the latter to be displaced with use of a wind-up drum. However, since the wire openings once clogged with the sintering material are extremely difficult to free from the latter, the resulting sintering material layer cannot be stably retained in an initially expected segregated state.
On the other hand, in Japanese Unexamined Patent Publication No. 5-311257, a method is disclosed wherein a mixture of a combustible gas and a low-melting material is sprayed onto an upper portion of a sintering material layer deposited on a pallet with use of a sintering material in common use. In this instance, the heat of the combustible gas and the low-melting material are successively supplied to the upper portion of that layer. This means that sintering reaction improves in the upper layer portion, leading to a sintered ore of high strength. Such method, however, has rather a different but serious problem in that supply of a combustible gas, mixing of a low-melting material therewith, and transportation of and spraying of both gas and material require added equipment, thus entailing increased cost for installation or remolding of the new or existing equipment.
Furthermore, Japanese Unexamined Patent Publication No. 58-133333 discloses loading a sintering material on a pallet by applying a magnetic force, through an electromagnet disposed on a loading device, to a sintering material on dropping. More specifically, the electromagnet is secured to a roll feeder or the like located downwardly of an ore supplying hopper, and the magnetic force is given via the electromagnet to the content of ferrous metal (Fe) present in the sintering material being loaded. The drop speed of Fe is hence reduced with gentle loading of the sintering material ensured. Fine particles are relatively susceptible to higher magnetization than are coarse particles, and therefore, the lower the drop speed is, the particles become finer. This denotes that the coarse particles drop on the pallet earlier and enter a lower portion of a sintering material layer, whereas the fine particles enter an upper portion of that layer. The sintering material is thus placed in segregated condition.
However, in a system having an electromagnet fixed to a rotary feeder, a sintering material segregated in its particle sizes on such rotary feeder is turned upside down when it is charged from the latter feeder to a sloping chute. This would often invite some adversely affected results. It is thought here that the magnetically attracted Fe content might possibly be separated by repeating an on-off manipulation of the electromagnet. In such instance, magnetic field generation and Fe separation are unfeasible in continuous fashion so that stable segregation is not attainable with poor efficiency.
In order to solve the foregoing problems of the prior art, the present invention has for its object to provide a method of the magnetic loading of a sintering material which can be practiced substantially without added equipment for avoiding marred adherence of a sintering material as well as added equipment for incorporating secondary materials that results in increased investment and which can also be implemented, with minimized formation of a sintered ore of undesirable brittleness in an upper portion of a sintering material layer as experienced with conventional practice, by applying a magnetic force to the sintering material immediately before loading on a pallet so as to desirably or intentionally vary the material composition and particle size distribution in a direction corresponding to the height of the sintering material layer. This unique construction contributes greatly to enhanced yield and productivity of a sintered ore.
In achieving the aforementioned object, the present invention in a first aspect provides a method of the magnetic loading of a sintering material wherein a starting sintering material is cut out of an ore supplying hopper by means of a drum feeder and is then charged onto a pallet mounted on a sintering apparatus of a Dwight-Lloyd type to thereby bring the starting sintering material into layered form on the pallet, the method comprising: applying a magnetic force to the starting sintering material having been cut through the drum feeder and being continuously flowed as the starting sintering material is slidably dropped out of a tip of a sloping chute of a plate type onto the pallet, the magnetic force being generated by a cylindrical magnetic drum located downwardly of the sloping chute; and causing magnetically susceptible sinterable substances present in the starting sintering material to be magnetically attracted toward and attached to a lower portion of the sintering material layer, while segregating fine substances of low drop speed present in the starting sintering material in that lower portion, whereby both the magnetically susceptible sinterable substances and the fine substances of low drop speed are segregated in large amounts in an upper portion of the sintering material layer on the pallet by inverting the starting sintering material upside down when it is loaded on the pallet with use of the magnetic drum.
In a second aspect, the invention provides a method of the magnetic loading of a sintering material as defined in the first aspect, wherein part of the starting sintering material having become adherent to the magnetic drum is removed by a scraper disposed in abutting relation to the magnetic drum and is then recovered on the pallet.
In a third aspect, the invention provides a method of the magnetic loading of a sintering material as defined in the first aspect, wherein an endless belt is arranged in interengagement with the magnetic drum located downwardly of the plate-type sloping chute and also with a drum placed opposite to the magnetic drum, and part of the starting sintering material having been adherent to the endless belt is removed by a scraper held in abutting relation to the endless belt and is then recovered on the pallet.
In a fourth aspect, the invention provides a method of the magnetic loading of a sintering material as defined in any one of the first to third aspects, wherein an ancillary sloping chute is located beneath the plate-type sloping chute normally disposed in parallel spaced relation to the latter, the normal sloping chute being reciprocative between a position in which it is operative and an upwardly slant position in which it is retractive, the magnetic drum located downwardly of the normal sloping chute is horizontally reciprocative forward and backward, and the starting sintering material is adjusted such that the path of dropping from the ancillary sloping chute to the magnetic drum is prevented from becoming varied through horizontal reciprocation of the magnetic drum located downwardly of and correspondingly to the ancillary sloping chute when the starting sintering material is charged by the downward ancillary sloping chute during displacement of the normal sloping chute from its operative position to its upward retractive position so as to remove part of the starting sintering material having adhered thereto.
In a fifth aspect, the invention provides a method of the magnetic loading of a sintering material as defined in any one of the first to fourth aspects, wherein a permanent magnet is disposed downwardly of the plate-type sloping chute, and the speed at which the starting sintering material is dropped from the sloping chute to the magnetic drum is reduced by magnetization of, through the magnetic force of the permanent magnet, the starting sintering material while it is being dropped out of the sloping chute.
In a sixth aspect, the invention provides a method of the magnetic loading of a sintering material as defined in any one of the first to fifth aspects, wherein an auxiliary magnetic drum is arranged upstream of and oppositely to the magnetic drum located downwardly of the plate-type sloping chute, and magnetically susceptible sinterable substances present in the starting sintering material are magnetically attached to the auxiliary magnetic drum through its magnetic action, which sinterable substances have failed to get magnetically attracted to the magnetic drum during dropping between the magnetic drum and the auxiliary magnetic drum.
In a seventh aspect, the invention provides a method of the magnetic loading of a sintering material as defined in any one of the first to sixth aspects, wherein a first magnetic drum located downwardly of an upper sloping chute of a plate type and a second magnetic drum located downwardly of a lower magnetic drum of a plate type are serially arranged in a two-staged formation, and magnetically susceptible sinterable substances present in the starting sintering material having dropped out of the upper sloping chute are magnetically attached to the first magnetic drum by its magnetizing action, while magnetically susceptible sinterable substances having dropped out of the lower sloping chute are magnetically attached to the second magnetic drum through its magnetizing action.
In an eighth aspect, the invention provides a method of the magnetic loading of a sintering material wherein a starting sintering material is cut out of an ore supplying hopper by means of a drum feeder and is then charged onto a pallet mounted on a sintering apparatus of a Dwight-Lloyd type to thereby bring the upper portion of that layer deposited on the pallet, the method comprising: dropping the starting sintering material cut by the drum feeder out of a sloping chute of a belt conveyor type in which a magnetic drum is placed on a driving side and a separate drum on a driven side; causing magnetically susceptible sinterable substances present in starting sintering material to be magnetically attached to the magnetic drum through its magnetizing action; and then segregating the resultant sinterable substances, together with fine substances of low drop speed in the sintering material, in a lower portion of the sintering material layer while the magnetic drum is being rotated forward or backward, whereby the starting sintering material is loaded directly on the pallet from the belt conveyor-type sloping chute.
In a ninth aspect, the invention provides a method of the magnetic loading of a sintering material wherein a starting sintering material is cut out of an ore supplying hopper by means of a drum feeder and is then charged onto a pallet mounted on a sintering apparatus of a Dwight-Lloyd type to thereby bring the starting sintering material into layered form on the pallet, the method comprising: applying a magnetic force to the starting sintering material cut by the drum feeder, the magnetic force being generated from a magnetic drum positioned to rotate in a direction along which the starting sintering material is dropped; causing magnetically susceptible sinterable substances present in the starting sintering material to be magnetically attached to the magnetic drum; and then segregating the resultant sinterable substances together with fine substances present in the starting sintering material, whereby the starting sintering materials is loaded directly on the pallet from the magnetic drum.
In a tenth aspect, the invention provides a method of the magnetic loading of a sintering material as defined in any one of the first to ninth aspects, wherein the magnitude of magnetic force of the magnetic drum, or the number of revolution of the latter is adjusted depending on the target amount of the magnetically susceptible sinterable substances to be segregated in an upper portion of the sintering material layer loaded on the pallet.
In an eleventh aspect, the invention provides a method of the magnetic loading of a sintering material wherein a starting sintering material is cut out of an ore supplying hopper by means of a drum feeder and is then charged onto a pallet mounted on a sintering apparatus of a Dwight-Lloyd type to thereby bring the starting sintering material into layered form on the pallet, the method comprising: dropping the starting sintering material cut by the drum feeder out of a sloping chute of a plate type having a plurality of permanent magnets arrayed in a backwardly serially vertical posture; and causing magnetically susceptible sinterable substances present in the starting sintering material to be magnetically attached to the sloping chute; and then segregating the resultant sinterable substances, together with fine substances present in the starting sintering material, in a lower portion of the sintering material layer, whereby the starting sintering material is loaded directly on the pallet from the sloping chute.
In a twelfth aspect, the invention provides a method of the magnetic loading of a sintering material as defined in the eleventh aspect, wherein the magnitude of magnetic force of each of the permanent magnets is adjusted depending on the target amount of said magnetically susceptible sinterable substances to be segregated in an upper portion of the sintering material layer loaded on the pallet.
In a thirteenth aspect, the invention provides a method of the magnetic loading of a sintering material as defined in the eleventh aspect, wherein as the starting sintering material is dropped out of the plate-type sloping chute disposed such that the permanent magnets arrayed in a backwardly serially vertical posture are increased in their magnitudes of magnetic forces gradually from top to bottom, the magnetically susceptible sinterable substances are magnetically attached by the permanent magnets through their magnetic forces, whereby the starting sintering material is loaded directly on the pallet from the sloping chute.
In a fourteenth aspect, the invention provides a method of the magnetic loading of a sintering material as defined in the thirteenth aspect, wherein the strength of magnetic force of each of the permanent magnets is adjusted depending on the bulk density of the starting sintering material to be loaded on the pallet.